Facebook seems to have switched users on their platform to the @facebook.com email id on their profiles.
Basically, you would now see their Facebook email address when you check their profiles.
Facebook email accounts are connected to the username picked by the members of Facebook. Mine is Sushubh@facebook.com.
Here is a screenshot from my profile:
Of course, you can revert back to your preferred email account for your profile by editing the relevant section. This is just another thing you have to opt-out of.
Facebook spoke about this change:
As we announced back in April, we’ve been updating addresses on Facebook to make them consistent across our site. In addition to everyone receiving an address, we’re also rolling out a new setting that gives people the choice to decide which addresses they want to show on their timelines. Ever since the launch of timeline, people have had the ability to control what posts they want to show or hide on their own timelines, and today we’re extending that to other information they post, starting with the Facebook address.
This looks like the latest strategy from the company to lock users to their platform. Few people are likely to revert back to their primary email id on their profiles and this would mean that third party services would fetch this email address from their accounts. It also means that public users would try to communicate with them through Facebook instead of their preferred email platform.